1. Field of the Invention
The present invention relates to a piston for an internal combustion engine, having a piston base body and a piston ring element, whereby the piston base body has at least an inner region of a piston crown as well as a piston skirt, which is provided with pin bosses having pin bores, whereby the piston ring element has at least an outer region of a piston crown having a circumferential top land, and a circumferential ring belt provided with ring grooves. The present invention furthermore relates to a method for the production of such a piston.
2. The Prior Art
A piston of this type, as well as a method of this type, are known from DE 10 2007 005 268 A1. In this piston, the contact regions of the piston base body and of the piston ring element are structured in step shape or configured as a tongue-groove region, and the piston ring element is joined with the piston base body in non-releasable manner. In this way, the required tolerances for the joining method are adjusted, and canting of the two components is avoided.
This known design or this known method bring with them the result that a combustion chamber bowl is provided only in the piston base body, so that the bowl edge consists of the same material as the piston base body itself. In modern pistons, however, the piston crown and, in particular, the bowl edge, are subject to great mechanical and thermal stresses. For this reason, the use of correspondingly stress-withstanding steels is favored, so that in the piston of the stated type, the entire piston base body must necessarily consist of these materials. This brings with it not only high costs, but above all disadvantages in the mechanical processing during the course of production of the piston base body.
Furthermore, in the case of thermal joining methods, such as the welding method or soldering method that is preferred in the method of this type, significant inherent stresses build up, since the components shrink while they are cooling. These inherent stresses can only be reduced with difficulty in the case of axially circumferential seams such as those provided in the piston of this type, because of the shrinkage hindrance that necessarily results. For this reason, use of a ductile additional material is necessary, in order to avoid the occurrence of cracks during the joining process.
Particularly in the case of soldering methods or modern beam-welding methods, high demands are set with regard to fitting precision of the components to be joined. The gap widths of the joints between the components to be joined that are selected in these methods generally amount to less than 0.1 mm, frequently only 0.05 mm, since the beam diameter is correspondingly small in the case of modern beam-welding methods, for example. In the case of the piston of the stated type, the joining surfaces must be produced in multiple work cycles, by means of structuring the steps and their position relative to one another, thereby making great demands on the precision of the individual machining steps. This method is very complicated and therefore leads to increased production costs.